CN109817818B - Organic electroluminescent device and display device - Google Patents
Organic electroluminescent device and display device Download PDFInfo
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Abstract
The invention provides an organic electroluminescent device and a display device. The organic electroluminescent device comprises a first light-emitting layer and a second light-emitting layer, wherein the material of the first light-emitting layer comprises a first host material, a first sensitizer and a first dye, and the material of the second light-emitting layer comprises a second host material, a third host material, a second sensitizer and a second dye; the first host material can form an exciplex with the second host material or the third host material, and the second host material can form an exciplex with the third host material; the first sensitizer and the second sensitizer are both thermally activated delayed fluorescence materials; the first dye and the second dye are both resonance type thermal activation delayed fluorescence materials. According to the light-emitting layer of the organic electroluminescent device, the interface exciplex and the bulk exciplex are used as main materials, the TADF material is used as a sensitizer sensitization resonance type TADF material, the efficiency roll-off is obviously reduced, and the efficiency and the stability of the device are obviously improved.
Description
Technical Field
The invention relates to an organic electroluminescent device and a display device, and belongs to the technical field of organic electroluminescence.
Background
An Organic Light Emitting Diode (OLED) is a device that emits Light by current driving, and its main characteristic comes from the Light Emitting layer. When a proper voltage is applied, electrons and holes combine in the light-emitting layer to generate excitons, which emit light.
The current luminescent dyes used in the light emitting layer are mainly based on conventional fluorescent materials and phosphorescent materials. The traditional fluorescent material can only utilize 25% singlet excitons to emit light, and the low luminous efficiency is not beneficial to reducing the power consumption of the device. Although the phosphorescent material can achieve internal quantum efficiency of 100% at maximum, it is expensive and easily causes environmental pollution due to the inclusion of heavy metals, and thus it is difficult to be the first choice for a light-emitting material.
The Thermal Activated Delayed Fluorescence (TADF) material can absorb environmental heat to realize reverse intersystem crossing of triplet excitons to singlet states, and further emit fluorescence from the singlet states, thereby realizing 100% utilization of the excitons and avoiding the need of any heavy metal. However, the use of TADF material in the light-emitting layer tends to result in a severe roll-off in efficiency, a lower device efficiency and poor color purity.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the organic electroluminescent device, which can effectively improve the efficiency and the color purity of the device.
The invention also provides a display device which has good performance due to the organic electroluminescent device.
In order to achieve the above object, the present invention provides an organic electroluminescent device comprising a first light emitting layer and a second light emitting layer, wherein the material of the first light emitting layer comprises a first host material, a first sensitizer and a first dye, and the material of the second light emitting layer comprises a second host material, a third host material, a second sensitizer and a second dye; the first host material can form an exciplex with the second host material or with the third host material, and the second host material can form an exciplex with the third host material; the first sensitizer and the second sensitizer are both thermally activated delayed fluorescence materials; the first dye and the second dye are both resonance type thermally activated delayed fluorescence materials (resonance type TADF materials).
The organic electroluminescent device provided by the invention is provided with the two luminescent layers, so that the exciton recombination area is widened, the spectral stability is improved, and the efficiency roll-off is reduced. Because a bulk-phase exciplex is formed in one of the light emitting layers and an interface exciplex is formed between the two light emitting layers, triplet excitons can be converted into singlet excitons to a great extent, the concentration of the triplet excitons is reduced, DET energy transfer (Dexter excitation transfer) between the host material and the dye is effectively inhibited, the efficiency roll-off is reduced, and the utilization rate of the excitons is improved.
Because the two light-emitting layers both adopt TADF materials as sensitizing agents, triplet excitons can be further converted into singlet excitons through reverse intersystem crossing, and then the energy is transferred to dyes through Forrester, so that the exciton utilization rate is further improved.
In particular, when a resonance type TADF material is used as a dye in both of the two light-emitting layers, the light-emitting efficiency of the organic electroluminescent device can be further improved. Presumably, the resonance TADF material has a planar aromatic rigid structure, so that it has a good carrier transport property, and in addition, the triplet excitons of the resonance TADF material also undergo intersystem crossing to its own singlet state, so that the singlet and triplet energies in the organic electroluminescent device are fully utilized, and the efficiency roll-off of the device is significantly reduced, and the luminous efficiency is significantly improved.
And the resonance type TADF material has stable plane aromatic rigid structure, and has very good structural stability because no obvious donor group and acceptor group exist in the molecule, thereby also improving the stability of the organic electroluminescent device to a certain extent.
In addition, when a resonance type TADF material is used as a dye in both of the light-emitting layers, a narrower light-emitting spectrum can be obtained, and color purity can be improved. Presumably, due to the specific chemical structure of the resonant TADF material, no significant intramolecular charge transfer excited state exists in the interior of the molecule, and finally the organic electroluminescent device has a very narrow full width at half maximum FWHM, which is better than that of the non-resonant TADF material as a dye.
The invention also provides a display device comprising the organic electroluminescent device. The display device may be specifically a display device such as an OLED display, and any product or component with a display function including the display device, such as a television, a digital camera, a mobile phone, a tablet computer, and a navigator. The display device has the same advantages of the organic electroluminescent device compared with the prior art, and the description is omitted here.
According to the organic electroluminescent device provided by the invention, the interface exciplex and the bulk exciplex of the double luminescent layers are used as a main material, the TADF material is used as a sensitizer, and the resonance TADF material is used as a dye, so that the efficiency roll-off of the organic electroluminescent device is obviously reduced, the efficiency and the stability of the device are obviously improved, and the color purity can be improved.
The display device provided by the invention also has good performance due to the organic electroluminescent device.
Drawings
FIG. 1 is a schematic diagram illustrating the energy transfer principle of an electroluminescence process according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present embodiment provides an organic electroluminescent device, including a first light emitting layer and a second light emitting layer, where a material of the first light emitting layer includes a first host material, a first sensitizer, and a first dye, and a material of the second light emitting layer includes a second host material, a third host material, a second sensitizer, and a second dye; the first host material can form an exciplex with the second host material or with the third host material, and the second host material can form an exciplex with the third host material; the first sensitizer and the second sensitizer are both thermally activated delayed fluorescence materials; the first dye and the second dye are both resonance type thermal activation delayed fluorescence materials.
An organic electroluminescent device generally includes an anode and a cathode, and an organic material layer between the two electrodes. The organic material layer may be divided into a plurality of regions such as a hole transport region, a light emitting layer, and an electron transport region. The hole transport region may be a hole transport layer having a single-layer structure, or may be a multi-layer structure including at least two layers of a hole injection layer, a hole transport layer, and an electron blocking layer. The electron transport region may be a single-layer electron transport layer, or may be a multilayer structure including at least two layers of an electron injection layer, an electron transport layer, and a hole blocking layer.
The present embodiment is not particularly limited to the above-mentioned manufacturing process and material selection for the anode, the cathode and the organic material layer except for the light-emitting layer, for example, two electrodes may be formed by sputtering or depositing a material used as an electrode on the substrate, wherein the anode may be Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), tin dioxide (SnO)2) An oxide transparent conductive material such as zinc oxide (ZnO), or any combination thereof; the cathode can adopt metals or alloys such as magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag) and the like, and any combination of the metals or alloys; the organic material layer other than the light emitting layer may be formed over the electrode by vacuum thermal evaporation, spin coating, printing, or the like. The compound used as the organic material layer may be an organic small molecule, an organic large molecule, or a polymer, and combinations thereof.
Specifically for the light emitting layer, the organic electroluminescent device of the present embodiment has two light emitting layers, wherein the second light emitting layer forms a bulk-exciplex compound through the second host material and the third host material, and an interfacial exciplex is formed between the first light emitting layer and the second light emitting layer; the two luminescent layers both use TADF materials as a sensitizer and resonance type TADF materials as a dye.
As shown in fig. 1, when a voltage is applied between the cathode and the anode, the bulk exciplex and the interfacial exciplex are formed and together serve as a host material, part of triplet energy of the two exciplexes can return to a singlet state through reverse system-mediated hopping (RISC), and then be transferred to the TADF material serving as a sensitizer through a Forrester energy transfer manner, and then the triplet state of the TADF material can also return to the singlet state through a reverse system-mediated crossing process, and further transfer energy to the resonance TADF material (i.e., the resonance-type dye in fig. 1). Since the resonance type TADF material can cause intersystem crossing, light emission can be performed by using both singlet excitons and excitons that transition from a triplet state to a self singlet state. In the whole light emitting process, the Dexter energy transfer between the triplet state and the triplet state is inhibited to a great extent, and annihilation (TTA) between triplet excitons at high concentration is avoided, so that the efficiency roll-off can be reduced, and the device performance is improved.
The TADF material is generally considered to be reported in Nature 2012 by Adachi et al of kyushu university of japan at the earliest. Such materials have a very small singlet-triplet energy gap (Δ E)ST) Under the action of ambient heat, the triplet excitons can be effectively up-converted to singlet excitons for light emission. Conventional thermally activated delayed fluorescence materials generally have a distorted molecular structure and have physically separated donor groups and acceptor groups.
The resonance type thermal activation delayed fluorescence material is a compound which is reported in recent years and also has thermal activation delayed fluorescence characteristics, generally has a planar aromatic rigid structure, and does not have obvious donor groups and acceptor groups in molecules. In the present invention, for the purpose of distinction, the conventional thermally activated delayed fluorescence material is referred to as a "non-resonant thermally activated delayed fluorescence material" and is simply referred to as a "non-resonant TADF material".
In this embodiment, the resonant TADF material used for both luminescent layers is not particularly limited. Preferably, the resonance type TADF material used as a dye in the present embodiment preferably has a structure as shown in the following formula [1] to further improve the device efficiency:
wherein, X is selected from B, P, P-O, P-S, SiR1One of (1); r1Selected from H, substituted or unsubstituted C1～C36Alkyl, substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30The heteroaryl group of (a);
a is selected from substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30Heteroaryl, substituted or unsubstituted C6～C30Arylamino of (a);
M1and M2Each independently selected from H, substituted or unsubstituted C1～C36Alkyl, substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30The heteroaryl group of (a);
adjacent X, A, M1、M2Is connected in a ring and comprises X in said ring;
a is an integer of 1-12;
when the substituent exists in the groups, the substituent is independently selected from halogen, cyano and C1～C10Alkyl of (C)2～C6Alkenyl of, C1～C6Alkoxy or thioalkoxy of C6～C30Aryl of (C)3～C30One or more of the heteroaryl groups of (a).
It is understood that when X is independently selected from P O, P S, the P atom is independently bonded to M1And M2Connecting; when X is selected from SiR1When Si atom is bonded to M1And M2And (4) connecting.
It is emphasized that in the above formula [1]]In the structure of (1), a are X, M1、M2Can be selected independently of each other, i.e. comprising X, M1、M2May be the same or different, M in each unit1、M2And may be the same or different. In addition, in the present embodiment, at least one resonant TADF material used in the luminescent layer passes through the adjacent X, A, M1、M2At least three of which are connected to form a ring.
Further, in the above formula [1]]In the structure of (1), adjacent X, A, M1、M2Three of which are connected to form a six-membered ring containing two heteroatoms; the hetero atoms are selected from two of B, P, Si, O, S, N and Se. Specifically, adjacent X, A, M1Can be joined to form a six-membered ring containing two heteroatoms, adjacent X, A, M2Can be joined to form a six-membered ring containing two heteroatoms, adjacent X, M1、M2Can be joined to form a six-membered ring containing two heteroatoms.
It is understood that one heteroatom in the six-membered ring is derived from X, i.e. specifically B, P, Si, and the other heteroatom is selected from one of O, S, N, Se. When the other heteroatom is N, the N atom, since it is trivalent, may be attached to an alkyl substituent in addition to a hydrogen atom, with specific substituents being cyano, C1～C10Alkyl or cycloalkyl of, C2～C6Alkenyl or cycloalkenyl of1～C6Alkoxy or thioalkoxy of C6～C30Aryl and C3～C30One or more of the heteroaryl groups of (a).
Considering that the preparation of the luminescent layer at the present stage mostly adopts an evaporation contact process, such as a multi-source co-evaporation method, the resonant TADF material with a molecular weight of 200-2000 is preferred in this embodiment, so as to avoid the evaporation difficulty caused by the excessively large molecular weight of the resonant TADF material.
As a way of controlling the molecular weight of the resonance type TADF material, a is defined as an integer of 1-6, i.e. the resonance type TADF material of the present embodiment may comprise 1-6 pieces of X, M1、M2The unit (2).
In the present embodiment, as the resonance TADF material of the dye, at least one of the compounds F-1 to F-29 having the following general formula may be selected, in particular, to improve the light-emitting efficiency of the organic electroluminescent device and reduce the efficiency roll-off:
wherein R is independently selected from hydrogen, halogen, cyano and C1～C10Alkyl of (C)2～C6Alkenyl of, C1～C6Alkoxy or thioalkoxy of C6～C30Aryl and C3～C30One or more of the heteroaryl groups of (a); y is independently selected from O, S, Se.
Still more preferably, the resonance type TADF material used in the two luminescent layers of the present embodiment may be selected from at least one of the following compounds M-1 to M-72:
in a resonant TADF molecule, the difference in resonance effect between different atoms causes spatial separation between HOMO and LUMO of the molecule on different atoms, and the overlapping area of orbitals is small, which in turn causes the difference in energy levels between singlet and triplet states of the resonant TADF molecule to be small, so that the resonant TADF material can undergo reverse intersystem crossing. Preferably, in the present embodiment, the difference between the energy levels of the singlet state and the triplet state of the resonant TADF material is 0.3eV or less, so that the intersystem crossing can be performed by absorbing the ambient heat.
It will be appreciated that to ensure a narrower half-width of the spectrum for better color purity of the device, the emission wavelengths of the first and second dyes should be close. Preferably, the difference between the emission wavelengths of the first and second dyes is no greater than 10 nm. In particular, the first dye and the second dye may be the same resonant TADF material to obtain a narrower spectral half-peak width, thereby providing excellent color purity of the device. In addition, the same resonance type TADF material is adopted for the first dye and the second dye, and the processing difficulty of the luminescent layer can be reduced.
The doping concentration of the dyes in the two light-emitting layers is reasonably controlled, and the efficiency of the device is further improved. Preferably, the doping concentration of the first dye in the light-emitting layer is 1 to 20 wt%, and especially 1 to 10 wt%. The doping concentration of the second dye in the luminescent layer is 1-20 wt%, especially 1-10 wt%.
Exciplexes are excited electron transfer complexes, specifically the interaction of an excited state of one molecule with a ground state of another molecule. It is understood that two host materials capable of forming an exciplex, one of which is a hole type material (electron donor type material) and the other of which is an electron type material (electron acceptor type material). In this embodiment, the second host material and the third host material can form a bulk-exciplex, so that generally one of the two can be a hole-type material and the other can be an electron-type material.
The first host material can form an interfacial exciplex with the second host material, or the first host material can form an interfacial exciplex with the third host material. Taking the example that the first host material can form an interface exciplex with the second host material, if the second host material is a hole-type material, the first host material is an electron-type material.
Among them, the following compounds H1-1 to H1-36 are preferable as the hole-type material:
the electronic type material is preferably the following compounds H2-1 to H2-20:
preferably, the difference in energy level between the singlet state and the triplet state of the interface exciplex formed between the first host material and the second host material (or the first host material and the third host material) is preferably less than 0.2eV, so that the triplet exciton absorption ambient heat undergoes faster transition back to the singlet state via the reverse intersystem hopping; the energy level difference between singlet state and triplet state of the bulk exciplex formed by the second host material and the third host material is preferably less than 0.2eV, so that triplet exciton absorption ambient heat undergoes faster transition back to singlet state via reverse intersystem transition.
In a specific implementation of this embodiment, the first host material and the second host material may be the same compound; or the first host material and the third host material may be the same compound, thereby facilitating the implementation of the vacuum evaporation process.
It is understood that if the first host material is a hole-type material, the light-emitting layer where the first host material is located may be disposed adjacent to the anode, and the other light-emitting layer may be disposed adjacent to the cathode, so that an exciplex is formed after the anode and the cathode are energized. If the first host material is an electron-type material, the light-emitting layer where the first host material is located may be disposed close to the cathode, and the other light-emitting layer may be disposed close to the anode.
In this embodiment, TADF material is used as the sensitizer for the two light emitting layers. The TADF material may be a conventional TADF material (non-resonant TADF material) or a resonant TADF material. In the implementation of this embodiment, the first sensitizer and the second sensitizer are both non-resonant TADF materials.
It will be appreciated that the non-resonant TADF materials used as the first and second sensitizers preferably have a small singlet-triplet energy level difference, ensuring a low barrier from triplet to singlet energy levels, to further improve exciton utilization and device efficiency. In a specific implementation, the first sensitizer and the second sensitizer are preferably non-resonant TADF materials with a singlet-triplet level difference of less than 0.3 eV.
Further, the difference in triplet energy levels between the first sensitizer and the second sensitizer is preferably not more than 0.2eV to reduce Dexter energy transfer between the first sensitizer and the second sensitizer.
The present embodiment is not particularly limited to the specific choice of the non-resonant TADF material used as the sensitizer, as long as the above requirements are satisfied. In particular, the non-resonant TADF materials used are preferably the following compounds T-1 to T-99.
Specifically, the materials of the first sensitizer and the second sensitizer may be different, for example, the first sensitizer is compound T-20, and the second sensitizer is compound T-19. Preferably, the first sensitizer and the second sensitizer are the same material, such as compound T-24. The two sensitizing agents are made of the same material, so that the operation is more convenient and the practicability is higher when the luminescent layer is formed from the production process.
The doping concentration of the sensitizing agents in the two light emitting layers is reasonably controlled, and the efficiency of the device is improved. Preferably, the doping concentration of the first sensitizer in the first light-emitting layer is 1-50 wt%, and especially can be controlled to be 10-50 wt%; and/or the doping concentration of the second sensitizer in the first light-emitting layer is 1-50 wt%, and especially can be controlled at 10-50 wt%.
In this embodiment, the thickness of each light-emitting layer can be controlled to be 1-50 nm, and generally 10-40 nm. In a specific implementation, the thicknesses of the two light emitting layers may be the same or different. Preferably, the sum of the thicknesses of the first light-emitting layer and the second light-emitting layer is controlled to be 10 to 60nm, and particularly 30 to 60 nm. The sum of the thicknesses of the two light-emitting layers is controlled within the range, so that the exciton recombination area formed between the two light-emitting layers can be ensured, the exciton recombination in the light-emitting layers is facilitated, the spectral stability is further ensured, and the efficiency roll-off can be reduced.
The embodiment also provides a display device comprising the organic electroluminescent device.
The display device can be specifically a display device such as an OLED display, and any product or component with a display function including the display device, such as a television, a digital camera, a mobile phone, a tablet computer, a navigator and the like. The display device has the same advantages as the organic electroluminescent device compared with the prior art, and the description is omitted here.
The technical solutions in the embodiments will be further described below with reference to specific embodiments, and it is obvious that the described specific embodiments are some embodiments, but not all embodiments, of the present invention.
Examples 1 to 9
Examples 1 to 9 each provide an organic electroluminescent device having a structure of ITO/NPB (40nm)/TCTA (10 nm)/double light-emitting layer/TPBI (30nm)/LiF (1nm)/Al (100nm), but the materials and thicknesses of the double light-emitting layers were different. The material composition of a specific dual emission layer is shown in table 1.
TABLE 1
The following performance measurements were performed on the organic electroluminescent devices in the above examples: under the same brightness, a Keithley K2400 digital source meter and a PR 655 spectral scanning brightness meter are used for measuring the starting voltage and the current efficiency of the organic electroluminescent device, and then the external quantum efficiency of the device under different brightness is calculated, wherein the full width at half maximum FWHM is 1000cd/m2The following measurements were made. Wherein the voltage is boosted at a rate of 0.1V per second to achieve a luminance of 1cd/m when the organic electroluminescent device is used2The voltage at that time is the turn-on voltage. The test results are shown in table 2 below.
TABLE 2
From the test results in table 2, it is found that when the light-emitting layer of the organic electroluminescent device uses the bulk-exciplex and the interfacial exciplex as the host materials, the TADF material as the sensitizer, and the resonance TADF material as the dye, the emission intensity was 5000cd/m2The external quantum efficiency is higher than 17.5 percent and is 10000cd/m2The external quantum efficiency is higher than 15.5%, the smaller efficiency roll-off is shown, and the maximum external quantum efficiency is more than 19.5%; the half-peak width is about 30nm, and the color purity is better. The technical scheme of the embodiment can have very high device efficiency, very low efficiency roll-off and very good color purity.
In particular, the devices of examples 1-6 were at 5000cd/m2The external quantum efficiency is higher than 19.0 percent and is 10000cd/m2The lower external quantum efficiency is more than 17.5%, the maximum external quantum efficiency is more than 20.0%, and smaller efficiency roll-off and higher external quantum efficiency are shown.
Comparing the device performance of examples 1 to 6 with that of example 7, it can be seen that the device performance is relatively better when the doping concentration of the first sensitizer in the first light-emitting layer is 10% to 50% and/or the doping concentration of the second sensitizer in the second light-emitting layer is 10% to 50%;
comparing the device performance of examples 1 to 6 with that of example 8, it can be seen that the device performance is relatively better when the doping concentration of the first dye in the first light emitting layer is 1% to 10%, and/or the doping concentration of the second dye in the second light emitting layer is 1% to 10%;
comparing the device performance of examples 1 to 6 with that of example 9, it can be seen that the device performance is relatively better when the sum of the thicknesses of the two light emitting layers is controlled to be 30nm to 60 nm.
Comparative example 1
Comparative example 1 provided an organic electroluminescent device substantially identical to the OLED device of example 2, except that the light-emitting layer of comparative example 1 was a single light-emitting layer having a thickness of 40nm, and the material of the single light-emitting layer was identical to that of the first light-emitting layer of example 2.
Comparative example 2
Comparative example 2 provided an organic electroluminescent device substantially identical to the OLED device of example 5 except that the light-emitting layer of comparative example 2 was a single light-emitting layer having a thickness of 50nm, the material of which was identical to that of the second light-emitting layer of example 5.
The material composition and thickness of the light-emitting layer in comparative examples 1-2 above are shown in table 3, and the results of the performance test are shown in table 4.
TABLE 3
TABLE 4
From the test results of Table 4 and referring to Table 2, it can be seen that the device of comparative example 1 has the maximum external quantum efficiency of 5000cd/m2And 10000cd/m2The external quantum efficiencies are all obviously lower than those of example 2; maximum external quantum efficiency, 5000cd/m for the device in comparative example 22And 10000cd/m2The external quantum efficiency is obviously lower than that of the
Example 5.
Therefore, by adopting the technical scheme of the dual light-emitting layer in the embodiment, the bulk-exciplex and the interface compound are used as the host materials, the TADF material is used as the sensitizer, and the resonance TADF material is used as the dye, the external quantum efficiency of the device can be remarkably improved, and the performance of the device can be improved.
Comparative example 3
The organic electroluminescent device provided in comparative example 3 has a structure substantially identical to that of the OLED device in example 2 except that the material of the light emitting layer is different, and the dyes in the first light emitting layer and the second light emitting layer in comparative example 3 are the following compounds D1 and D2 (conventional fluorescent materials), respectively. The material composition and thickness of the light emitting layer in the specific comparative example 3 are shown in table 3, and the performance test results are shown in table 4.
As is clear from the test results in Table 4 in combination with Table 2, in comparative example 3, in which the double light-emitting layer was used, the bulk exciplex and the interfacial exciplex were used as the host material, the TADF material was used as the sensitizer, but the resonance TADF material was not used as the dye, the maximum external quantum efficiency of the device, 5000cd/m2And 10000cd/m2The external quantum efficiencies are all significantly lower than in example 2. In addition, the half-peak width of the device in comparative example 3 is significantly larger than realExample 2.
Therefore, by adopting the technical scheme of the dual light-emitting layer in the embodiment, especially by using the resonance type TADF material as the dye, the external quantum efficiency of the device can be significantly improved, the color purity can be improved, and the overall performance of the device can be effectively improved.
In the description of the present invention, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. An organic electroluminescent device is characterized by comprising a first light-emitting layer and a second light-emitting layer, wherein the material of the first light-emitting layer comprises a first host material, a first sensitizer and a first dye, and the material of the second light-emitting layer comprises a second host material, a third host material, a second sensitizer and a second dye;
the first host material can form an exciplex with the second host material or with the third host material, and the second host material can form an exciplex with the third host material;
the first sensitizer and the second sensitizer are both thermally activated delayed fluorescence materials;
the first dye and the second dye are both resonance type thermal activation delayed fluorescence materials.
2. The organic electroluminescent device according to claim 1, wherein the resonance type thermally activated delayed fluorescence material has a structure represented by formula [1 ]:
wherein, X is selected from B, P, P-O, P-S, SiR1One of (1); r1Selected from H, substituted or unsubstituted C1～C36Alkyl, substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30The heteroaryl group of (a);
a is selected from substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30Heteroaryl, substituted or unsubstituted C6～C30Arylamino of (a);
M1and M2Each independently selected from H, substituted or unsubstituted C1～C36Alkyl, substituted or unsubstituted C6～C30Aryl, substituted or unsubstituted C3～C30The heteroaryl group of (a);
adjacent X, A, M1、M2Is connected in a ring and comprises X in said ring;
a is an integer of 1-12;
when R is1、A、M1Or M2Wherein when a substituent is present, the substituent is independently selected from the group consisting of halogen, cyano, and C1～C10Alkyl of (C)2～C6Alkenyl of, C1～C6Alkoxy or thioalkoxy of C6～C30Aryl of (C)3～C30One or more of the heteroaryl groups of (a).
3. The organic electroluminescent device of claim 2, wherein adjacent X, A, M1、M2Three of which are connected to form a six-membered ring containing two heteroatoms;
the heteroatom is selected from two of B, P, Si, O, S, N and Se.
4. The organic electroluminescent device according to claim 2 or 3, wherein the resonance type thermally activated delayed fluorescence material is at least one selected from compounds having the following general formula:
wherein R is independently selected from hydrogen, halogen, cyano and C1～C10Alkyl of (C)2～C6Alkenyl of, C1～C6Alkoxy or thioalkoxy of C6～C30Aryl and C3～C30One or more of the heteroaryl groups of (a); y is independently selected from O, S, Se.
5. The organic electroluminescent device according to claim 4, wherein the resonance type thermally activated delayed fluorescence material is selected from at least one of the following compounds:
6. the organic electroluminescent device according to claim 1, wherein the difference between the emission wavelengths of the first dye and the second dye is within 10 nm.
7. The organic electroluminescent device according to claim 6, wherein the doping concentration of the first dye in the first light emitting layer is 1 to 20 wt%; and/or the doping concentration of the second dye in the second light-emitting layer is 1-20 wt%.
8. The organic electroluminescent device according to claim 1, wherein the doping concentration of the first sensitizer in the first light-emitting layer is 1 to 50 wt%; and/or the doping concentration of the second sensitizer in the second light-emitting layer is 1-50 wt%.
9. The organic electroluminescent device according to claim 1, wherein the first light-emitting layer has a thickness of 1 to 50 nm; and/or the thickness of the second light-emitting layer is 1-50 nm.
10. A display device comprising the organic electroluminescent element as claimed in any one of claims 1 to 9.
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